title: Stress-vs-time signals allow the prediction of structurally catastrophic events during fracturing of immature cartilage and predetermine the biomechanical, biochemical, and structural impairment.
abstract: OBJECTIVE
  Trauma-associated cartilage fractures occur in children and adolescents with clinically significant incidence. Several studies investigated biomechanical injury by compressive forces but the injury-related stress has not been investigated extensively. In this study, we hypothesized that the biomechanical stress occurring during compressive injury predetermines the biomechanical, biochemical, and structural consequences. We specifically investigated whether the stress-vs-time signal correlated with the injurious damage and may allow prediction of cartilage matrix fracturing.
  
  
  METHODS
  Superficial and deeper zones disks (SZDs, DZDs; immature bovine cartilage) were biomechanically characterized, injured (50% compression, 100%/s strain-rate), and re-characterized. Correlations of the quantified functional, biochemical and histological damage with biomechanical parameters were zonally investigated.
  
  
  RESULTS
  Injured SZDs exhibited decreased dynamic stiffness (by 93.04±1.72%), unresolvable equilibrium moduli, structural damage (2.0±0.5 on a 5-point-damage-scale), and 1.78-fold increased sGAG loss. DZDs remained intact. Measured stress-vs-time-curves during injury displayed 4 distinct shapes, which correlated with histological damage (p<0.001), loss of dynamic stiffness and sGAG (p<0.05). Damage prediction in a blinded experiment using stress-vs-time grades was 100%-correct and sensitive to differentiate single/complex matrix disruptions. Correlations of the dissipated energy and maximum stress rise with the extent of biomechanical and biochemical damage reached significance when SZDs and DZDs were analyzed as zonal composites but not separately.
  
  
  CONCLUSIONS
  The biomechanical stress that occurs during compressive injury predetermines the biomechanical, biochemical, and structural consequences and, thus, the structural and functional damage during cartilage fracturing. A novel biomechanical method based on the interpretation of compressive yielding allows the accurate prediction of the extent of structural damage.
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany; Massachusetts Institute of Technology, Center for Biomedical Engineering, Cambridge, MA 02319, USA. Electronic address: berndrolauffs@googlemail.com.
authors.forename: Bernd
authors.initials: B
authors.lastname: Rolauffs
authors.affiliation: Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland 4226, Australia; Anatomical Institute, Christian-Albrechts-University, 24098 Kiel, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Kurz
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany.
authors.forename: Tino
authors.initials: T
authors.lastname: Felka
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Rothdiener
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Uynuk-Ool
authors.affiliation: Department of Orthopaedic and Trauma Surgery, Elblandklinikum Riesa, 01589 Riesa, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Aurich
authors.affiliation: Massachusetts Institute of Technology, Center for Biomedical Engineering, Cambridge, MA 02319, USA.
authors.forename: Eliot
authors.initials: E
authors.lastname: Frank
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Bahrs
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Badke
authors.affiliation: Siegfried Weller Institute for Trauma Research, BG Trauma Clinic, Eberhard Karls University, 72076 Tuebingen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stöckle
authors.affiliation: Department of Urology, Eberhard Karls University, 72072 Tuebingen, Germany.
authors.forename: Wilhelm K
authors.initials: WK
authors.lastname: Aicher
authors.affiliation: Massachusetts Institute of Technology, Center for Biomedical Engineering, Cambridge, MA 02319, USA.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Grodzinsky
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D002417:Cattle; D006025:Glycosaminoglycans / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D046509:Tissue Culture Techniques
chemical_list: D006025:Glycosaminoglycans
keywords: Articular cartilage; Bilayer composite; Bio-mechanics; Cartilage; Cartilage fracture; Compressive injury; Damage prediction; Functional damage; GAG loss; Histology; Immature; Immature cartilage; Impact injury; Injury; Peak stress; Post-traumatic osteoarthritis; Stress; Stress time signal; Stress-vs-time; Structural damage; Zonal damage; Zonal function; Zone